Each of U.S. Pat. Nos. 4,186,996 and 4,273,413 and 4,534,616 discloses a connector assembly for a diode that disconnectably connects the diode to an optical fiber. In the connector assembly, optical emission from the diode is transmitted successively through different transparent materials having different indices of optical refraction. A difficulty associated with the connector assembly is that the emission is scattered at the boundary between transparent materials of different indices. Another difficulty is that the emission can reflect from surfaces of the materials or from a junction of one of the materials with an air gap. Particularly, if the diode is a laser diode, and the emission is reflected backward at low angles of incidence to the reflecting surface, such backward reflections can enter the laser diode and cause instability of the diode.